This invention relates to a multi-layered polishing pad having separable layers for modifying an exposed surface of a semiconductor wafer.
In the course of integrated circuit manufacture, a semiconductor wafer typically undergoes numerous processing steps, including deposition, patterning, and etching steps. After selected steps in this process, it is often desirable, and often necessary, to periodically modify or planarize the wafer surface to achieve a pre-determined level of surface xe2x80x9cplanarityxe2x80x9d and/or xe2x80x9cuniformityxe2x80x9d.
Chemical mechanical polishing (CMP) is a known method of planarizing the surface of a semiconductor wafer. In CMP planarization, a semiconductor wafer is typically mounted on a carrier or polishing head. The exposed surface of the wafer is then placed against a rotating polishing pad in the presence of polishing slurries or fluids. Suitable polishing pads include slurry pads for use with polishing slurries as well as fixed abrasive pads for use with polishing fluids.
During CMP planarization, the polishing pads are periodically replaced. For a fixed abrasive pad, the wafer wears away the abrasive contact surface of the pad. Thus, the fixed abrasive surface is gradually worn away or used up by the polishing process and, after a sufficient number of wafers have been polished, the fixed abrasive pad must be replaced. For a slurry pad, the wafer both mechanically and thermally damages the contacting surface of the polishing pad and causes the surface to become smoother and less effective. Therefore, slurry pads must regularly be xe2x80x9cconditionedxe2x80x9d to restore a roughened texture to the contacting surface and when such conditioning can no longer be done, these pads must also be replaced.
These polishing pads typically are constructed as a multi-layered stack of materials that are chosen in order to provide a good planarization of the features on the semiconductor wafer. The portion of the stack attached to the polishing surface is known as the xe2x80x9csub-padxe2x80x9d. These sub-pads may be as simple as foam layered with adhesive, or may be complex layerings of rigid and resilient materials, adhesives, film carriers and/or other materials. In general, the cost of the sub-pad tends to represent a large portion of the overall cost of the polishing pad.
When the polishing surface of the pad wears out and is no longer usable, the polishing pad must be replaced, which typically entails removal of the entire pad from the polishing machine. Since polishing pads are typically adhered directly to the aluminum or stainless steel platen of the polishing machine, removal from the platen is often time consuming and difficult. In addition, since the abrasive polishing surface of the pad usually wears out faster than the sub-pad layers, replacement of the whole polishing pad under these circumstances is more expensive than necessary.
The present invention provides a polishing pad suitable for semiconductor wafer planarization that reduces the effort, time and cost involved with pad replacement. The polishing pad includes a sub-pad having at least one layer and a polishing surface. At least one release layer is interposed between the polishing surface and at least some portion of the sub-pad. When the polishing surface of the pad becomes unusable, the surface may easily be removed at a release layer leaving at least a portion of the sub-pad still attached to the polishing device to which the polishing pad is mounted during a polishing process. A new polishing surface may then be attached to the remaining portion of the sub-pad. Release layers may be interposed between different layers of a multi-layer sub-pad, if desired. Thus, only the portions of the polishing pad that require replacement are removed, thereby simplifying and reducing the cost of polishing pad replacement.
Throughout this application, the following definitions apply:
xe2x80x9cSurface modificationxe2x80x9d refers to wafer surface treatment processes, such as polishing and planarizing;
xe2x80x9cRigid elementxe2x80x9d refers to an element which is of higher modulus than the resilient element and which deforms in flexure;
xe2x80x9cResilient elementxe2x80x9d refers to an element which supports the rigid element, elastically deforming in compression;
xe2x80x9cModulusxe2x80x9d refers to the elastic modulus or Young""s Modulus of a material; for a resilient material it is measured using a dynamic compressive test in the thickness direction of the material, whereas for a rigid material it is measured using a static tension test in the plane of the material;
xe2x80x9cFixed abrasive elementxe2x80x9d refers to an integral abrasive element, such as an abrasive article, that is substantially free of unattached abrasive particles except as may be generated during modification of the surface of the workpiece (e.g., planarization);
xe2x80x9cThree-dimensionalxe2x80x9d when used to describe a fixed abrasive element refers to a fixed abrasive element, particularly a fixed abrasive article, having numerous abrasive particles extending throughout at least a portion of its thickness such that removing some of the particles at the surface during planarization exposes additional abrasive particles capable of performing the planarization function;
xe2x80x9cTexturedxe2x80x9d when used to describe a fixed abrasive element refers to a fixed abrasive element, particularly a fixed abrasive article, having raised portions and recessed portions in which at least the raised portions contain abrasive particles and binder;
xe2x80x9cAbrasive compositexe2x80x9d refers to one of a plurality of shaped bodies which collectively provide a textured, three-dimensional abrasive element comprising abrasive particles and binder; the abrasive particles may be in the form of abrasive agglomerates; and
xe2x80x9cPrecisely shaped abrasive compositexe2x80x9d refers to an abrasive composite having a molded shape that is the inverse of the mold cavity which is retained after the composite has been removed from the mold; preferably, the composite is substantially free of abrasive particles protruding beyond the exposed surfaces of the shape before the abrasive article has been used, as described in U.S. Pat. No. 5,152,917 (Pieper et al.).